In semiconductor manufacturing, optical metrology is typically used for measuring and evaluating properties such as optical properties, shapes of nano patterns, and the like, of nano samples in real time by a non-destructive manner or a non-contact manner. For example, after a periodic grating is formed on a semiconductor wafer, an optical metrology system may be used to determine a profile of the periodic grating.
For example, after a plurality of wafers is sequentially loaded into one semiconductor manufacturing apparatus, a specific semiconductor process may be performed on the wafers respectively. Some wafers sampled from the wafers processed by the processes may be measured by different measuring tools.
Because the sampling wafers may be measured in a defined order by several measuring tools, not by one measuring tool, an error between measurement values may occur due to variations in optical components and light beam profiles between the measuring tools. In order to compensate the error by the tool variation, final data may be corrected by an offset. However, because the final data may include an error caused by the tool variation as well as process variation, even though the final data is corrected by the offset, the error may not be completely compensated.